Method for surface-treating forging member

ABSTRACT

An objective of the present invention is to provide an innovative method for surface-treating a forging member, the method exhibiting unprecedented operations and effects. The present invention is a method for surface-treating a forging member ( 1 ), wherein a slurry ( 4 ) comprising a mixture of a liquid ( 2 ) and an abrasive ( 3 ) is mixed with pressurized air and sprayed on a surface ( 1   a ) of the forging member ( 1 ), and innumerable recesses ( 5 ) measuring 0.5-2.00 μm in depth and 75-150 μm in opening width are provided on the surface ( 1   a ) of the forging member ( 1 ).

TECHNICAL FIELD

The present invention relates to a method for surface-treating a forgingmember.

BACKGROUND ART

Cold-forging, adopted as a method for manufacturing machine components,is limited to a greater extent than manufacturing by cutting in terms ofthe forms that can be manufactured. Nevertheless, cold-forging hasnumerous merits, making it possible to mass-produce the same forms,obtain higher strength, shorten machining time, and economize onmaterials, among other benefits.

It has traditionally been desirable to lubricate the surface of acolumnar forging member serving as a workpiece to be cold-forged (suchlubrication commonly being referred to as bonderizing, which is alubricating-film-attaching treatment) and firmly anchor a lubricationfilm on the surface of the forging member in order to improve thedie-releasing properties, to prevent damage to the mold due to heat orcontact pressure arising during processing, as well as to prevent damageto the forging member itself.

The inventor(s) proposed workpiece surface treatment devices disclosedin JP-A 2007-38309 and U.S. Pat. No. 5,523,507. Prior to attaching alubricating film to the surface of a forging member serving as aworkpiece, these devices spray a slurry comprising a mixture of a liquidand an abrasive to perform a wet-blasting treatment on the surface ofthe forging member.

By performing this wet-blasting treatment, removal of oxidized films,oil, and other pollutants attached to the surface of the forging memberis reliably and satisfactorily performed, and minute irregularities areformed on the surface of the forging member, whereby a lubricating filmis satisfactorily established so as to not readily peel off.

PRIOR ART DOCUMENTS Patent Documents

[Patent Document 1] JP-A 2007-38309

[Patent Document 2] Patent No. 5523507

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

As a result of further research and development regarding surfacetreatment of forging members such as is described above, the inventor(s)developed an innovative method for surface-treating a forging member,the method exhibiting unprecedented operations and effects.

Means for Solving the Problem

The main points of the present invention are described below withreference to the attached drawings.

The present invention relates to a method for surface-treating a forgingmember 1, the method being characterized in that a slurry 4 comprising amixture of a liquid 2 and an abrasive 3 is mixed with pressurized airand sprayed on a surface 1 a of the forging member 1, and innumerablerecesses 5 measuring 0.5-2.00 μm in depth and 75-150 μm in opening widthare provided on the surface 1 a of the forging member 1.

The present invention also relates to a method for surface-treating aforging member according to the first aspect, characterized in that theforging member 1 is made from chromium-molybdenum steel.

The present invention also relates to a method for surface-treating aforging member according to either of the first and second aspects,characterized in that a stainless-steel abrasive having an averageparticle diameter of approximately 150 μm is adopted as the abrasive 3.

Effect of the Invention

Because the present invention is configured as described above, thisinnovative method for surface-treating a forging member exhibits thesatisfactory establishment of a lubricating film so that the lubricatingfilm formed on the surface of the forging member does not readily peeloff, among other unprecedented operations and effects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a device for implementing the method forsurface-treating a forging member as pertains to the present example;

FIG. 2 is a schematic view showing the state of a surface-treatedforging member in the present example;

FIG. 3 is a partial enlarged view of the surface of the surface-treatedforging member in the present example;

FIG. 4 is a schematic view illustrating conditions of testing thatindicates the effectiveness of the present example;

FIG. 5 is a schematic view showing a test of the performance of aforging member using a forward rod/backward can extrusion tester;

FIG. 6 is a schematic view showing a test of the performance of aforging member using a forward rod/backward can extrusion tester;

FIG. 7 is a schematic view illustrating test results that indicate theeffectiveness of the present example;

FIG. 8 is a schematic view illustrating test results that indicate theeffectiveness of the present example;

FIG. 9 is a schematic view illustrating test results that indicate theeffectiveness of the present example;

FIG. 10 is a schematic view illustrating test results that indicate theeffectiveness of the present example;

FIG. 11 is a schematic view illustrating test results that indicate theeffectiveness of the present example;

FIG. 12 is a schematic view illustrating test results that indicate theeffectiveness of the present example; and

FIG. 13 is a schematic view illustrating test results that indicate theeffectiveness of the present example.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention are briefly describedbelow with reference to the diagrams while indicating the action of thepresent invention.

In the present invention, a slurry 4 comprising a mixture of a liquid 2and an abrasive 3 is mixed with pressurized air and sprayed on a surfaceof a forging member 1, and innumerable recesses 5 measuring 0.5-2.00 μmin depth and 75-150 μm in opening width are provided on the surface ofthe forging member 1.

The forging member 1 comprising the innumerable recesses 5 does notreadily lose lubricity once the lubricating treatment has beenperformed, and is highly exceptional as a raw material for forging.

Examples

A specific example of the present invention is described below withreference to the diagrams.

The present example is a method for surface-treating a transportedcolumnar forging member 1, a surface treatment being performed on asurface 1 a of the forging member 1. The forging member 1 is columnarand is made from metal (chromium-molybdenum steel). In the presentdocument, “columnar” refers to a long shape of circular cross-section;in the broadest sense, “columnar” includes cylindrical shapes havinghollow interiors.

Specifically, the method for surface-treating a forging member 1 aspertains to the present example is performed using the surface treatmentdevice 10 disclosed in U.S. Pat. No. 5,523,507.

The surface treatment device 10 is equipped with a transportation part12 for transporting the columnar forging member 1 on a base 11, asillustrated in FIG. 1, and a surface treatment part for performingwet-blasting treatment and other treatments on the forging member 1transported by the transportation part 12.

Specifically, the surface treatment part is configured from awet-blasting treatment part 13, and other treatment parts (a cleaningtreatment part, a hot-water washing part, a lubrication treatment part,and a drying treatment part) (not shown).

The wet-blasting treatment part 13 is provided to the base 11, overwhich the columnar forging member 1 is caused to pass, as shown inFIG. 1. The wet-blasting treatment part 13 is equipped with aslurry-spraying part 14, a slurry reservoir part 15 arranged at aposition below the slurry-spraying part 14, and a slurry-transportingpart 17 for transporting a slurry 4 from the slurry reservoir part 15 tothe slurry-spraying part 14 via a pump device 16, and is configured suchthat the slurry 4 sprayed from the slurry-spraying part 14 is deliveredto the slurry reservoir part 15 and reused.

The slurry-spraying part 14 is configured from a wide spray nozzlearranged above the transportation part 12 for transporting the columnarforging member 1, as shown in FIG. 1.

The slurry-transporting part 17 described above is connected to thespray nozzle, and a compressed-air-transporting part 19 provided in aseparate circuit and extending from a compressed-air-supplying part 18is connected to the spray nozzle, the spray nozzle being configured suchthat the slurry 4 supplied from the slurry-transporting part 17 isaccelerated by compressed air supplied from thecompressed-air-transporting part 19 and is sprayed from the spray nozzleat a prescribed spraying speed.

The slurry 4 used in the present example is a mixture of a liquid 2 anda fine-particle abrasive 3.

The surface treatment used on the forging member 1 using the surfacetreatment device 10 comprising the configuration described above willnow be described.

The surface 1 a of the columnar forging member 1 transported by thetransporting part 12 is appropriately treated by the surface treatmentpart.

Specifically, once the columnar forging member 1 transported by thetransporting part 12 passes the wet-blasting treatment part 13, theslurry 4 is sprayed to blast the entire surface 1 a (peripheral andlengthwise-end surfaces) of the columnar forging member 1, andinnumerable minute recesses 5 are formed on the entire surface 1 a(peripheral and lengthwise-end surfaces).

Next, once the columnar forging member 1 that has been blasted by thewet-blasting treatment part 13 passes the cleaning treatment part, thecolumnar forging member 1 is sprayed with cleaning fluid, whereby theforging member 1 is washed with water (to remove the slurry, chips, andthe like).

Next, once the columnar forging member 1 that has been washed by thecleaning treatment part passes the hot-water washing part, the columnarforging member 1 is sprayed with hot water, whereby the forging member 1is washed with water and heat-treated.

Next, once the columnar forging member 1 that has been washed andheat-treated by the hot-water washing part passes the lubricationtreatment part, the columnar forging member 1 is coated with lubricant(e.g., metallic soap), whereby the forging member 1 is lubricated.

Next, once the columnar forging member 1 that has been lubricated by thelubrication treatment part passes the drying treatment part, thecolumnar forging member 1 is blown with hot air, whereby the forgingmember 1 is dried (solidifying the lubricant), and a lubricating film isformed on the entire surface 1 a (peripheral and lengthwise-endsurfaces) of the columnar forging member 1.

The columnar forging member 1 that has been dried by the dryingtreatment part is then guided out of the surface treatment device 10 bya guiding part. The lubricating film is satisfactorily established onthe entire surface 1 a (peripheral and lengthwise-end surfaces) of theguided columnar forging member 1.

In the present example, innumerable (approximately 74,000) recesses 5(pyramid-shaped recesses) are formed on the surface 1 a of the forgingmember 1 having the raw materials and size described below, the recesses5 measuring 0.5-2.00 μm in depth, 75-150 μm in opening width, and0.006-0.023 mm² in area, the forging member 1 being highly exceptional.

This is confirmed by the testing described below.

Specifically, first, an abrasive A (50-μm stainless-steel abrasive), anabrasive B (150-μm stainless-steel abrasive), an abrasive C (210-μmstainless-steel abrasive), an abrasive D (320-μm stainless-steelabrasive), an abrasive E (250-μm alumina abrasive), and an abrasive F(300-μm steel abrasive) are prepared. The abrasives A-E are used totreat the forging member 1 (chromium-molybdenum steel, SCM420, 19.9 mmin diameter, 20 mm long, approximately 1,030 mm² in surface area) usingthe surface treatment device 10 described above (the abrasive F is usedto perform shot-blasting), and the amounts of the resulting forgingmember 1 extruded forward and backward are measured using a forwardrod/backward can extrusion tester(see FIGS. 4 and 5).

FIG. 7 shows the relationship between the abrasives A-F and the forwardextrusion amount, and FIG. 8 shows the relationship between theabrasives A-F and the backward extrusion amount.

When the punch stroke in forward rod/backward can extrusion is fixed,the frictional resistance of the surface decreases in correspondencewith an increase in the forward extrusion amount and a decrease in thebackward extrusion amount; ordering the abrasive B, the abrasive C, theabrasive D, the abrasive E, the abrasive F, and the abrasive A in thestated order results in the best forward extrusion amount and backwardextrusion amount as well as low frictional resistance of the surface.

Specifically, a forging member 1 treated using the abrasive B has moreforward elongation and less backward elongation than does a forgingmember 1 treated using another abrasive; accordingly, it was evidentthat the frictional resistance in the surface 1 a of the forging member1 treated using the abrasive B is low. It is apparent from these resultsthat the molding load is strongly affected by the abrasive used.

FIG. 9 shows the relationship between the maximum load duringcold-forging molding and the forward extrusion amount.

The forging member 1 treated using abrasive B described above has alower maximum load during cold-forging molding than does a forgingmember 1 treated using another abrasive.

Specifically, the forging member 1 comprising a surface 1 a in which ahigh forward extrusion amount is produced results in a lower maximumload during cold-forging molding, the maximum load during cold-forgingmolding and the extrusion amounts being approximately inverselyproportional, as predicted.

FIG. 10 shows the relationship between the forward extrusion amount andthe depth (H) of the recesses 5 produced in the end surfaces of theforging member 1 when surface treatment is performed on the forgingmember 1 using the abrasives A-F, and FIG. 11 shows the relationshipbetween the forward extrusion amount and the opening width (W) of therecesses 5 produced in the end surfaces of the forging member 1 whensurface treatment is performed on the forging member 1 using theabrasives A-F.

As is apparent from FIG. 10, the depth of the recesses 5 produced bytreatment using the abrasive B is 0.5 μm when the air pressure is 0.2MPa, and is 1.5 μm when the air pressure is 0.4 MPa. As is apparent fromFIG. 11, the opening width of the recesses 5 produced by treatment usingthe abrasive B is 150 μm when the air pressure is 0.2 MPa, and is 140 μmwhen the air pressure is 0.4 MPa.

FIG. 12 shows the relationship between the forward extrusion amount andthe depth (H) of the recesses 5 produced in the side surface of theforging member 1 when surface treatment is performed on the forgingmember 1 using the abrasives A-F, and FIG. 13 shows the relationshipbetween the forward extrusion amount and the opening width (W) of therecesses 5 produced in the side surface of the forging member 1 whensurface treatment is performed on the forging member 1 using theabrasives A-F.

As is apparent from FIG. 12, the depth of the recesses 5 produced bytreatment using the abrasive B is 0.5 μm when the air pressure is 0.2MPa, and is 2.00 μm when the air pressure is 0.4 MPa. As is apparentfrom FIG. 13, the opening width of the recesses 5 produced by treatmentusing the abrasive B is 75 μm when the air pressure is 0.2 MPa, and is125 μm when the air pressure is 0.4 MPa.

The testing described above makes it possible to confirm that a forgingmember 1 treated using an abrasive B determined to be optimal andcomprising innumerable recesses 5 produced in a surface 1 a of theforging member 1, the recesses 5 measuring 0.5-2.00 μm in depth and75-150 μm in opening width, does not readily lose lubricity once alubricating treatment has been performed, and is highly exceptional as araw material for cold-forging.

Because the present example is configured as described above, a slurry 4comprising a mixture of a liquid 2 and an abrasive 3 is mixed withpressurized air and sprayed on a surface of a forging member 1, andinnumerable recesses 5 measuring 0.5-2.00 μm in depth and 75-150 μm inopening width are provided on the surface of the forging member 1.

The forging member 1 comprising the innumerable recesses 5 does notreadily lose lubricity once the lubricating treatment has beenperformed, and is highly exceptional as a raw material for forging.

Because the forging member 1 is made from chromium-molybdenum steel, thepresent example can reliably exhibit the operations and effectsdescribed above.

Because a stainless-steel abrasive having an average particle diameterof approximately 150 μm is adopted as the abrasive 3, the presentexample can reliably exhibit the operations and effects described above.

The present invention is not limited to the present example; thespecific configuration of the configuration requirements can beoptimized.

1. A method for surface-treating a forging member, characterized in that a slurry comprising a mixture of a liquid and an abrasive is mixed with pressurized air and sprayed on a surface of the forging member, and innumerable recesses measuring 0.5-2.00 μm in depth and 75-150 μm in opening width are provided on the surface of the forging member.
 2. The method for surface-treating a forging member according to claim 1, characterized in that the forging member is made from chromium-molybdenum steel.
 3. The method for surface-treating a forging member according to claim 1, characterized in that a stainless-steel abrasive having an average particle diameter of approximately 150 μm is adopted as the abrasive.
 4. The method for surface-treating a forging member according to claim 2, characterized in that a stainless-steel abrasive having an average particle diameter of approximately 150 μm is adopted as the abrasive. 